The present invention relates generally to an improved apparatus and system for monitoring and controlling the operation of individual work stations within a sanding system having a plurality of such stations functioning in combination with a continuous feed system such as an endless conveyor belt or roll feed. Other continuous feed systems, such as reciprocating systems or rotary feed systems are applicable. Such systems are in wide use today, and typically employ abrasive workpiece surfacing heads, such as drum heads and platen heads. These heads are arranged serially adjacent to and typically elevated from the surface of the conveyor, and treat the workpieces as they move along the conveyor between individual working stations disposed adjacent to the belt path. The present invention may be characterized as one wherein the stock removal occurring in individual work stations is carefully monitored, and wherein the quantity or magnitude of stock removal is referenced or indexed from the individual workpieces.
In sanding systems of the type described, proper working head adjustment is essential to maintain proper material removal targets preserve and extend the lifetime of the abrasive belts, and reduce and/or maintain proper power consumption. The systems also preserve the quality of finish (scratch removal) on the finished work. In this connection, the useful life of an individual belt within the multi-station system may be extended through proper and continuous monitoring of head elevation, thereby controlling the amount of stock removal at each station. A workpiece typically enters the system and is initially contacted and abraded by a coarse abrasive belt operating in the initial or first work station. Most of the stock removal occurs in the coarser stations, with later stations being typically and primarily employed for scratch removal and finish quality improvement. In order to preserve the quality and extend the lifetime of the relatively fine grit abrasive belts, care must be taken so as to avoid exceeding the removal capability of the finer grit belts. When care is taken to assure adequate stock removal at the early station or stations, the belt life of the subsequent fine-grit stations is substantially extended. Consistent with these objectives, care is taken to monitor the amount of material removal at each station along the continuous feed mechanism. More particularly, the datum plane for workpiece comparison purposes is that thickness targeted for workpieces as they exit the final work station in the series.
As abrasive belts constantly experience wear, care must be taken to reposition or adjust the working height of each working abrasive head in order to continuously maintain proper system balance and operation. Being subject to more aggressive action, abrasive belts with coarse grit tend to change caliper more rapidly than the finer belts, and hence constant or at least frequent adjustment of the stock removal heads is essential. Furthermore, as the abrasive belts employing finer grit change caliper or otherwise experience wear, they too must be adjustably positioned so as to maintain consistent and proper stock and accordingly scratch removal.
An additional cause of uneven belt wear and/or uneven sanding performance is in the tendency for wide-belt sanding heads to fall out of planar parallel relationship with the plane defined by the workpiece conveyor. For example, one or more of the sanding heads may, over time, displace out of parallel relationship with the workpiece conveyor top surface, thereby causing one side of the sanding belt to come into contact with the workpiece more heavily than a second laterally opposed side of the sanding belt. Such a situation results in uneven sanding of the workpiece, as well as uneven wear upon the sanding belt.
Whenever replacement of an abrasive belt is indicated, it is necessary to shut the entire machine operation down and undertake such replacement as required. Inasmuch as the abrasive belts with the finer grits are highly susceptible to damage from running in an overload condition, frequency of belt replacement may be minimized if care is taken to assure that adequate stock removal occurs at the coarse-grit station or stations. In other words, by maintaining adequate and proper stock removal at the appropriate working station, belt wear for the scratch removal stations is substantially reduced and optimum system performance and workpiece quality are maintained.